Mobile communication devices have become increasingly common in current society for providing wireless communication services. The prevalence of these mobile communication devices is driven in part by the many functions that are now enabled on such devices. Increased processing capabilities in such devices means that mobile communication devices have evolved from being pure communication tools into sophisticated mobile multimedia centers that enable enhanced user experiences.
The redefined user experience requires higher data rates offered by wireless communication technologies, such as fifth generation new radio (5G-NR) and Wi-Fi that typically operates in higher frequency spectrums. To achieve higher data rates with increased robustness in the higher frequency spectrums, the mobile communication devices may employ multiple antennas to enable multiple-input multiple-output (MIMO) and/or beamforming operations. Sophisticated power amplifiers (PAs) may be employed to increase output power of radio frequency (RF) signals (e.g., maintaining sufficient energy per bit) prior to transmitting the RF signals from the multiple antennas. However, the increased number of antennas and PAs can lead to increased power dissipation in the mobile communication devices, thus compromising overall performance and user experiences.
Envelope tracking (ET) is a power management technology designed to improve efficiency levels of the PAs to help reduce power dissipation in the mobile communication devices. As the name suggests, an ET system receives an ET target voltage(s) associated with a time-variant target voltage envelope and generates an ET modulated voltage(s) having a time-variant voltage envelope that keeps track of the time-variant target voltage envelope. Accordingly, the PAs can be configured to amplify the RF signals based on the ET modulated voltage(s). Given that the time-variant target voltage envelope of the ET target voltage(s) may be correlated with time-variant amplitudes of the RF signals, the PAs may operate at improved linearity and efficiency if the ET modulated voltage(s) can closely track the ET target voltage(s) at all times. However, the ET modulate voltage(s) may deviate from the ET target voltage(s) from time to time due to cross over distortion, thus compromising linear performance of the PAs. As such, it may be desirable to dynamically detect and reduce the cross over distortion to help maintain linearity and efficiency in the PAs.